Regulation of Cell Motility on Polymer Substrates via "Dynamic," Cell Internalizable, Ligand Microinterfaces

Abstract

In vivo, motile epidermal tissues frequently encounter ligand microinterfaces that are dynamic, owing to rapid cell-mediated substrate phagocytosis. In this study, we have examined cell motility phenomena in response to the adhesion ligand, collagen, which was presented on cell-internalizable 400-nm colloidal gold microcarriers. Normal human keratinocytes were seeded onto collagen-adsorbed poly(lactide-co-glycolide) (PLGA) films that were predeposited with varying densities of the ligand-associated microcarriers (LAMs), such that the overall ligand density and the ligand loading per microcarrier were invariant. Cells seeded on LAMs exhibited rapid and distinct cytoskeletal redistribution resulting in numerous filopodial extensions, indicative of activation of cell motility processes. We report that the population-averaged cell migration rate of cells, mu, was increased from 2 microm2/min on collagen substrates lacking the microcarriers, to approximately 50 microm2/min on collagen presenting LAMs. An increase in LAM density to 1.2 LAMs per microm2 was found to maximize mu, as well as the directional persistence and speed of cell migration, whereas very high LAM densities saturated cell internalization and diminished migration rates. The cell-LAM interactions essential to enhanced migration were ligand-activated, as mu; values were reduced 400% on internalizable microcarriers lacking ligands; moreover, cooperative ligand elicitation was possible, for example, when 10 microg/mL soluble fibronectin was introduced as a costimulant of keratinocytes, yielding the highest reported mu values (80 microm2/min) on collagen LAM-PLGA substrates. Notably, cell migration rates were severely repressed when cell internalization processes were challenged through covalent conjugation of ligand carriers to the substrate, indicating that signals from cell-LAM binding alone were inadequate for elevated levels of cell migration. Further analysis indicated that the presence of LAMs did not alter the protease-resistant adhesivity between the cell and the underlying substrate, suggesting that the activation governing ligand interactions likely arose at the cell-LAM interface rather than the cell-substrate interface. This study highlights the novel use of secondary ligand-presenting microscale/nanoscale depots at polymer substrates to elicit, via dynamic cell internalization processes, significantly enhanced levels of cell migration over traditional interfaces with ligand-bearing substrates.

Tumor-Immune Interaction, Surgical Treatment, and Cancer Recurrence in a Mathematical Model of Melanoma

“…The linear diffusion coefficient for human keratinocytes was measured between .002 and .07 mm 2 day −1 in [34]. Assuming that melanoma cells achieve a similar rate of diffusion at maximum density yields in the range 7.0×10 −7 –4.0×10 −9 , using the range of densities reported in [33].…”

“…However, given that measurements for keratinocytes and endothelial cells fall within the same rough range, .002–.07 [34] and .000864–.070848, respectively [42],[43], we can reasonably assume a similar range for immune cells.…”

Coating nanothickness degradable films on nanocrystalline hydroxyapatite particles to improve the bonding strength between nanohydroxyapatite and degradable polymer matrix

“…Aliphatic polyesters are an important class of biodegradable polymers for bone repair. Polylactic acid (PLA), polyglycolic acid (PGA), and their copolymer poly(dl‐lactide‐ co ‐glycolide) (PLGA) have been well‐studied for bone tissue repair and regenerations applications 11–13. Despite a well‐defined safety profile for biomedical applications, literature data have indicated that degradation through hydrolysis mechanisms may cause adverse effects, such as aseptic sinus, painful swell, and bone resorption surrounding the implant, possibly due to the release and accumulation of acidic degradation products in the local tissue 14–16.…”

“…Polylactic acid (PLA), polyglycolic acid (PGA), and their copolymer poly(dl-lactide-coglycolide) (PLGA) have been well-studied for bone tissue repair and regenerations applications. [11][12][13] Despite a well-defined safety profile for biomedical applications, literature data have indicated that degradation through hydrolysis mechanisms may cause adverse effects, such as aseptic sinus, painful swell, and bone resorption surrounding the implant, possibly due to the release and accumulation of acidic degradation products in the local tissue. [14][15][16] Consequently, these implants exhibited excellent bone biocompatibility initially following implantation which then decreased dramatically as a function of implant degradation.…”

Plakoglobin suppresses keratinocyte motility through both cell–cell adhesion-dependent and -independent mechanisms

“…The colloidal gold migration assay was modified from a published protocol (22). Keratinocytes in single-cell suspension were plated onto colloidal gold-coated coverslips and incubated at 37°C for 18 h. Images were taken with a Leica (Deerfield, IL) DMR microscope͞Orca Hamamatsu (Ichinocho, Japan) digital camera system, and the area of individual tracks were measured by using OPENLAB (Improvision, Lexington, MA).…”